Various types of nail coating compositions are used by consumers today. By "nail coating composition" we mean a coating useful on nails for such purposes as changing the cosmetic appearance of nails, strengthening nails and hardening nails. Nail coating compositions include for example nail polishes, nail lacquers, top coats, base coats, nail strengtheners, nail hardeners, and nail polish quick dry products. Nail coating compositions typically contain one or more film formers in combination with other formulation additives such as solvents, coalescent agents, plasticizers, thickeners, suspension aids, and pigments.
One of the most popular film formers used today in nail coating compositions is nitrocellulose. Nitrocellulose is typically used in nail coating compositions as a primary film former in combination with a secondary film former such as toluene sulfonamide formaldehyde. The secondary film former is added to the nail coating composition to improve such properties as application, wear, and gloss. Although nitrocellulose has excellent pigment wetting capabilities, and forms a film which dries quickly, has high gloss, good hardness, and good resistance to abrasion and chemicals, it has disadvantages. For example, formulations containing nitrocellulose tend to discolor the nails and over time tend to drop in viscosity and lose the ability to form a hard film. Also, for solubility reasons, nitrocellulose is undesirably formulated with organic solvents such as ethyl acetate, methyl ethyl ketone, and toluene. These organic solvents are undesirable because they tend to be flammable and adversely affect air quality. Organic solvents also tend to discolor the nails, and make them brittle.
Because of these problems, nail formulators have investigated developing film formers for use in aqueous nail coating compositions. Most approaches have involved using a blend or dispersion of polymers which will form a film from an aqueous medium. For example, polyurethanes and polyacrylates have been used in aqueous nail coating compositions. However, these polymers tend to have inferior pigment wetting properties, and tend to form films which are not as durable, and have poor resistance to chemicals and abrasion.
JP 06-298624A has attempted to overcome these deficiencies of aqueous nail coating compositions by using as a film former an emulsion of dispersed particles having two polymer phases. The aqueous emulsion contains an inner A-phase polymer prepared from at least one type of monomer selected from alkyl methacrylic acid esters, aromatic vinyl compounds or monomers having two or more polymerizable unsaturated groups. The outer B-phase polymer consists of a copolymer prepared from at least one monomer selected from alkyl methacrylic acid esters, aromatic vinyl compounds, or monomers having two or more polymerizable unsaturated groups, and at least one type of monomer selected from a monomer containing a hydroxyl group, or amide group. The B-phase polymer has a weight average molecular weight of 200,000 or greater.
However, JP 06-298624A does not disclose that by controlling the degree of hydrophobicity in the polymer phases, an aqueous nail coating composition can be produced which has improved resistance to chemicals and abrasion. JP 06-298624A also does not address the problem of removeability of aqueous nail coating compositions. As detailed herein, removeability of aqueous nail coating compositions with conventional nail polish removers has been a problem. More particularly, improving removeability of an aqueous nail coating composition, without adversely affecting the chemical and abrasion resistance of the coating has been difficult.
Therefore, it is desirable to provide an aqueous nail coating composition which has improved resistance to chemicals and abrasion. It is also preferable to provide an aqueous nail coating composition which has improved removeability. The present invention addresses these problems by incorporating into an aqueous nail coating composition a film forming agent containing certain multi-phase polymers.